A372714 a(n) = tau(3*n-1) = A000005(3*n-1).

2, 2, 4, 2, 4, 2, 6, 2, 4, 2, 6, 4, 4, 2, 6, 2, 6, 2, 8, 2, 4, 4, 6, 2, 4, 4, 10, 2, 4, 2, 6, 4, 6, 2, 8, 2, 8, 2, 6, 4, 4, 4, 8, 2, 4, 2, 12, 4, 4, 2, 8, 4, 4, 4, 6, 2, 8, 2, 10, 2, 8, 4, 6, 2, 4, 2, 12, 4, 4, 4, 6, 4, 4, 4, 12, 2, 8, 2, 6, 2, 6, 6, 8, 2, 4, 2

Offset: 1

Author

Vaclav Kotesovec, May 11 2024

Keywords

• nonn

Crossrefs

Cf. A372713, A372715.

Cf. A000005, A099777, A099774.

Programs

Mathematica

Table[DivisorSigma[0, 3*n-1], {n, 1, 150}]

Formula

Sum_{k=1..n} a(k) ~ 2*n * (log(n) + 2*gamma - 1 + 2*log(3)) / 3, where gamma is the Euler-Mascheroni constant A001620.